Real-time 节点提供一个实时索引。通过这些节点索引的数据提供查询。real-time节点将定期将他们收集的数据转移到同一跨域时间的Historical节点。 使用zookeeper监控传输和MySQL存储的元数据转移。一旦转移,转移的部分从real-time节点中删除。
运行类
io.druid.cli.Main server realtime
Segment传播过程
Firehose
See Firehose.
Plumber
See Plumber
Extending the code
Realtime integration is intended to be extended in two ways:
- Connect to data streams from varied systems (Firehose)
- Adjust the publishing strategy to match your needs (Plumber)
The expectations are that the former will be very common and something that users of Druid will do on a fairly regular basis. Most users will probably never have to deal with the latter form of customization. Indeed, we hope that all potential use cases can be packaged up as part of Druid proper without requiring proprietary customization.
Given those expectations, adding a firehose is straightforward and completely encapsulated inside of the interface. Adding a plumber is more involved and requires understanding of how the system works to get right, it’s not impossible, but it’s not intended that individuals new to Druid will be able to do it immediately.